The C-076 compounds are a series of compounds which are isolated from the fermentation broth of Streptomyces avermitilis. The morphological characteristics of the culture, as well as the fermentation methods and process of isolation of the C-076 compounds is described in the West German published patent Application Ser. No. 27,170,407. Based on taxonomic studies, the microorganisms capable of producing these C-076 compounds are of a new species of the genus Streptomyces, which has been named Streptomyces avermitilis. One such culture, isolated from soil is designated MA-4680 in the culture collection of Merck & Co., Inc., Rahway, N.J. A C-076 producing sample of this culture has been deposited in the permanent culture collection of the Fermentation Section of the Northern Utilization Research Branch, U.S. Department of Agriculture at Peoria, Ill., and has been assigned the accession number NRRL 8165. A sample of NRRL 8165 has also been deposited, without restriction as to availability, in the permanent culture collection of the American Type Culture Collection at 12301 Parklawn Drive, Rockville, Md. 20852, and has been assigned the accession number ATCC 31,267.
C-076 producing mutants of Streptomyces avermitilis may be obtained by natural selection or those produced by mutating agents including X-ray irradiation, ultraviolet irradation, nitrogen mustard or like treatments, and such are also included within the ambit of this invention.
One example of such an organism is a strain of Streptomyces avermitilis MA 4848 which was isolated after irradiation with ultraviolet light of Streptomyces avermitilis MA 4680. A lyophilized tube and a frozen vial of this culture has been deposited in the permanent culture collection of the American Type Culture Collection, and they have been assigned the accession numbers 31272 and 31271 respectively. Slightly higher fermentation yields of C-076 have been obtained using this frozen stock as inoculum.
The compounds having the following structure: ##STR1## wherein R is the 4'-(.alpha.-L-oleandrosyl)-.alpha.-L-oleandrose group of the structure: ##STR2## and wherein the broken line indicates a single or double bond; R.sub.1 is hydroxy and is present only when said broken line indicates a single bond;
R.sub.2 is iso-propyl or sec-butyl; and PA1 R.sub.3 is methoxy or hydroxy.
There are eight different C-076 compounds and they are given the designations A1a, A1b, A2a, A2b, B1a, B1b, B2a, B2b, based upon the structure of the individual compounds.
With reference to the R.sub.1, R.sub.2 and R.sub.3 groups of the above structural formula, the individual C-076 compounds are set forth below:
______________________________________ R.sub.1 R.sub.2 R.sub.3 ______________________________________ A1a Double Bond ##STR3## OCH.sub.3 A1b Double Bond ##STR4## OCH.sub.3 A2a OH ##STR5## OCH.sub.3 A2b OH ##STR6## OCH.sub.3 B1a Double Bond ##STR7## OH B1b Double Bond ##STR8## OH B2a OH ##STR9## OH B2b OH ##STR10## OH ______________________________________
The C-076 compounds are generally isolated as mixtures of a and b components. Such compounds differ only in the nature of the R.sub.2 substituent and the minor structural differences have been found to have very little effect on the isolation procedures, chemical reactivity and biological activity of such compounds.
In addition, derivatives of the C-076 compounds have been prepared. In particular, the 22,23-dihydro derivatives of the 1-series of compounds have been found to have particularly advanageous biological properties. The 22,23-dihydro derivatives are prepared by selectively hydrogenating the 22,23 unsaturated prescursor. That is such compounds are prepared from the C-076 A1/A1b and C-076 B1a/B1b pair of compounds. The 22,23 dihydro compounds and their preparation are described in European published patent application Ser. No. 8300435.1. This, of course, requires that the C-076 A1a/A1b and B1a/B1b pairs be separated from the A2a/A2b and B2a/B2b pairs of compounds, and then reduced to prepare the dihydro derivatives. The main problem encountered with this procedure is that the A2a/A2b and B2a/B2b compounds remain unused, and in effect wasted.
The process of the instant invention removes this waste by converting the unused compounds into the 22,23-unsaturated precursors of the biologically preferred compounds, or into the even more biologically preferred 22,23-dihydro derivatives.